The present invention relates to automatic transmissions for land vehicles and, more particularly, to a pump-priming device for an automatic transmission fluid pump.
Fluid pumps in automatic transmission systems are generally positive displacement pumps driven by the engine of the vehicle wherein the transmission is installed. A positive displacement pump is one, which has the same output per revolution regardless of pump speed or hydraulic pressure already developed in the system. Thus, it is necessary to regulate automatic transmission fluid (hereinafter “ATF”) pressure so it does not get too high and damage other components. A basic pressure regulator valve employs a piston and a spring that compresses at a specific pressure to allow some ATF to flow back to the pump reservoir or sump bypassing the hydraulic circuit and reducing system pressure. By using a pressure regulator valve with a spring calibrated to a pressure lower than the pump's output, a generally constant pressure can be maintained in the hydraulic system during operation. Of course, given the continuous flow requirements of the hydraulic system, a consistent flow of ATF from the sump to the pump is critical to the proper function and lubrication of the transmission.
CHRYSLER automatic transmissions such as the series 727, 904, and 42 to 47RE transmissions (hereinafter “CHRYSLER transmissions”) utilized in rear wheel drive vehicles are known in the transmission repair industry to exhibit characteristic malfunctions, which are related to insufficient automatic transmission fluid (hereinafter “ATF”) flow to the pump at low engine speeds. The resulting service complaints in CHRYSLER vehicles include engine stall on transmission engagement, slow torque converter charge at engine idle, buzzing sounds from hydraulic valves, and pump noise.
Thus, the present invention has been developed to resolve these problems and other shortcomings of the prior art.